docs: def read_manifest():
      """Read existing configuration from MANIFEST.in.
  
      We use that to ignore anything the MANIFEST.in ignores.
      """
      # XXX modifies global state, which is kind of evil
      if not os.path.isfile('MANIFEST.in'):
          return
      ignore, ignore_regexps = _get_ignore_from_manifest('MANIFEST.in')
      IGNORE.extend(ignore)
      IGNORE_REGEXPS.extend(ignore_regexps)